Which of the following compounds exists as a zwitterion?

The list given below contains essential amino acids that are basic $(X)$ and also non-essential amino acids that are neutral $(Y)$. Identify $X$ and $Y$ from the following list:
$a)$ Lysine
$b)$ Alanine
$c)$ Serine
$d)$ Arginine
$e)$ Tyrosine

Which of the following is an example of a sulphur-containing amino acid?

Which of the following amino acids is not optically active?

The structures of glycine and alanine are given below. Show the peptide linkage in glycylalanine.
$H_2N-CH_2-COOH$ (glycine);
$H_2N-CH(CH_3)-COOH$ (alanine)

Given below are two statements $:$
Statement $(I):$ On hydrolysis,oligopeptides give rise to a fewer number of $\alpha$-amino acids,while proteins give rise to a large number of $\beta$-amino acids.
Statement $(II):$ Natural proteins are denatured by acids,which convert the water-soluble form of fibrous proteins to their water-insoluble form.
In the light of the above statements,choose the most appropriate answer from the options given below $:$